1. Technical Field of the Invention
The present invention relates to novolak epoxy resins having low viscosity which are useful as electric and electronic materials such as adhesives, paints, insulating materials, laminates and the like, epoxy resin compositions using such resins, and resin-sealed type semiconductor apparatuses.
2. Description of the Related Art
As an epoxy resin used as an electric and electronic material, particularly as an epoxy resin used for insulating a semiconductor element, there are known phenols novolak epoxy resins such as ortho cresol novolak resins and the like. On the other hand, recently, there is conducted a method in which an epoxy resin having low viscosity is used in an epoxy resin composition having high filler content, along with change in form of a semiconductor package such as reduction in thickness thereof and the like. For example, epoxy resins having low viscosity such as di-functional biphenyl epoxy resins and the like are used recently. Also, regarding phenols novolak epoxy resins typically including an ortho cresol novolak resin, a technology has been developed for obtaining an epoxy resin having sharp molecular distribution in which the binuclear compound content is low and the tri- to hexa-nuclear compound content is high, and epoxy resins have been obtained having low viscosity and high heat-resistance simultaneously. Technologies for obtaining such an epoxy resin having sharp molecular distribution in which the tri- to hexa-nuclear compound content is high are described in Japanese Patent Application Laid-Open (JP-A) Nos. 1-190722, 2-88628, 4-220422, 9-216932 and the like.
Conversely, as the novolak epoxy resin having high binuclear compound content, epoxy resins having low softening temperature are commercially available. For example, as such an ortho cresol novolak epoxy resin, "SUMIEPOXY ESCN-195LL" (trade name: manufactured by Sumitomo Chemical Co., Ltd.) and the like are known. In actuality, when this ortho cresol novolak epoxy resin is used for example in an epoxy resin composition for insulating a semiconductor wherein filler content is high in the composition, sufficiently low viscosity is not obtained.